In those sensory systems where regeneration of the sensory processes are slow to non-existent, e.g., vision and audition, age appears to be more of a physiological than a pathological state. On the other hand, in systems such as the cutaneous senses or the chemical senses, where the regeneration of neurological structure and function is considerable, pathological states seem better to account for the sensory defects encountered than does physiological involution. In order to test the hypothesis, the physiological involution versus pathological impairment, we propose to assess the receptive processes, by means of measurement of receptor sensitivity and distribution, the afferent conducting processes by means of assessing the dispersion of compound action potentials to mechanical stimuli, recorded per cutaneously, in primary afferents and the C-4 derivation on the scalp, and the decision process as elucidated by measurements of near threshold sensitivity by the 3 alternatives forced-choice method -a procedure incorporated in the Signal Detection Theory and psychophysical functions derived from magnitude estimates of suprathreshold intensities of stimulation.